High density inductively and capacitively coupled plasma chamber

ABSTRACT

An inductively coupled plasma chamber having a capacitor electrode during cleaning of the plasma chamber.

This application is a divisional of application Ser. No. 08/395,269,filed Feb. 28, 1995 now U.S. Pat. No. 5,523,261.

BACKGROUND OF THE INVENTION

A high plasma density chemical vapor deposition (CVD) is used to fillhigh aspect ratio spaces in-situ concurrent with a deposit to achievegap fill. High plasma density CVD is also used for etching. In highdensity CVD a potential is coupled inductively to ionize a gas (plasma)in a CVD chamber. Once ionized the plasma is referred to as aninductively coupled plasma (ICP). In one application ICP is used todeposit dielectric films for gap fill.

One problem encountered when using an ICP process is the inability toadequately clean residue from the chamber after each deposition run orafter each etch. In non-inductive systems chamber cleaning isaccomplished using capacitive coupling of an electrical potential to acleaning plasma which has been injected into the chamber. When using theinductively coupled design it is necessary to eliminate capacitivecoupling during the inductive coupling, thereby making it difficult forplasmas to clean the chamber surfaces, since without capacitive couplingefficient cleaning is not possible.

SUMMARY OF THE INVENTION

The invention is an apparatus capable of depositing a layer onto aworkpiece and capable of etching a portion from the workpiece and is themethod to clean the apparatus. The apparatus has a support memberextended from which is an enclosure portion. The support member and theenclosure portion form an enclosed chamber. The apparatus furthercomprises an external inductor which inductively ionizes a gas in thechamber during the etching and the deposition. The apparatus includes ameans for generating a capacitively coupled plasma in the enclosedchamber during cleaning and a means for eliminating capacitive couplingduring etching and depositing.

In the method of the invention a workpiece is inserted into a chamber.Gas injected into the chamber is inductively ionized. A chemicalprocess, such as an etch or a deposition, is performed on the workpieceusing the ionized gas. This chemical process creates debris, such asbyproducts from the chemical process and residue, on a surface of thechamber. Plasma is then injected into the chamber and a potential iscapacitively coupled to the plasma. The capacitively coupled plasmaloosens the debris from chamber surfaces and the loosened debris is thenremoved from the chamber.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 is a cross sectional view of a chemical vapor deposition chamberof the invention.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 is cross sectional view of an inductively coupled plasma chamber1 of the invention. A workpiece, typically a substrate 5, is supportedon a support member 10. An inner wall 15 extends from the support member10, typically near a periphery of the support member, to form anenclosed chamber 20. An outer wall 25 is concentric to and distancedfrom the inner wall 15 such that a void 30 or gap exists between theinner 15 and outer 25 walls. The support member 10, the inner wall 15,and the outer wall 25 are made from insulative materials. An inductorcoil 35 is positioned exterior to the outer wall 25 surrounding theouter wall 25. The inductor coil 35 may or may not be physicallyattached to the outer wall 25. During deposition or etching of thesubstrate 5 deposition or etch gases are injected into the enclosedchamber 20. The gases are inductively ionized by the inductor coil 35when current flows through the inductor coil 35.

Following the deposition or etching the enclosed chamber 20 is cleaned.During cleaning a plasma is generated in the enclosed chamber 20 and anelectrical potential is capacitively coupled to the plasma by acapacitor having a first electrode formed in the void 30 and having asecond electrode 36 positioned underlying the substrate 5 when thesubstrate 5 is positioned in the chamber 20. It should be noted that theexact position of the second electrode 36 may vary without departingfrom the inventive aspect. The charged plasma loosens debris, typicallyresidue or byproducts produced during etching or deposition, frominterior surfaces 40 of the enclosed chamber 20. The debris is thenpumped out of the chamber. During cleaning the inductor 35 is turned offand no current flows therein.

In a first embodiment a conductive liquid, such as mercury or otherliquid metal, is injected into the void 30 to form the first electrode36. Other materials which may be used are liquid polymers, organic orinorganic. Upon injection the conductive liquid comes into contact witha supply node 45 connectable to a supply potential. The supplypotential, which may supply alternating or direct current, charges theconductive liquid to an electrical potential. The charged conductiveliquid provides capacitive coupling for the cleaning plasma.

In the first embodiment the conductive liquid is removed from the voidsubsequent to the cleaning of the enclosed chamber in preparation forthe next deposition or etching step. Removal of the conductive liquideliminates problems that would occur if current was induced into theliquid metal during inductive coupling.

In a second embodiment the void 30 is filled with a material having avariable conductivity. A polymer whose conductivity may be varied by afew orders of magnitude in response to external energy such as heat,light, or ultrasonic energy is one example of a material having variableconductivity. Examples of polymers which may be used are polyacetylene,polythiophenes, polypyrroles, polyaniline, and PEO/PPO (poly propyleneoxide). An ionic solution, organic or inorganic, is an example of afurther material which may be used. In the present embodiment a polymeris the material of variable conductivity.

By controlling the conductivity of the polymer it becomes eitherelectrically insulative or electrically conductive. When it iselectrically conductive it forms the first electrode 36. Unlike theconductive liquid the polymer remains in the void 30 during both thecleaning step and the deposition and etching steps. However, theconductivity of the polymer is varied in order to create an insulator inthe void 30 during deposition and etching and in order to create aconductor during cleaning. Thus the polymer is charged during cleaningto capacitively couple a potential to the cleaning plasma and remainsunaffected by the induced voltage during deposition and etching.

The polymer is connected to supply node 45 which is connectable to thesupply potential. The supply potential is used to supply charge to thepolymer during cleaning.

In certain embodiments the polymer is connected to an energy source 50.The energy source 50 is used to control the conductivity of the polymer.

There are various methods of the invention used to change theconductivity of the polymer. The energy source 50 may be used to controlthe temperature of the polymer when the conductivity of the polymer issensitive to temperature. Typically, if the polymer is in an insulativestate sufficient increase of the temperature of the polymer changes itto its conductive state, in some cases this occurs when the temperatureis great enough to change the polymer from a solid to a liquid. If thistemperature increase is followed by a sufficient temperature decreasethe polymer is returned to the insulative state.

In a further method of the invention the energy source 50 suppliesultrasonic energy or light energy to the polymer to change it from anelectrical insulator to an electrical conductor. Of course the reverseis also true. Once the polymer is electrically conductive theapplication of ultrasonic or light energy may be terminated to returnthe polymer to the insulative state for further process steps.

In still a further method the polymer is doped to increase itsconductivity thereby changing it from an insulator to a conductor. Inthis application it is important to use one of the polymers in whichdoping is reversible in order to be able to also change the polymer froma conductor to an insulator.

In the case where the polymer remains in a solid state in both itsinsulative and conductive states it is possible to eliminate the outerwall 25.

The following article is herein incorporated by reference: NEWCONDUCTING POLYMER NETWORKS, by X. Andrieu, J. P. Boeuve and T. Vicedo,Journal of Power Sources, 43-44(1993) pages 445-451.

Thus the invention provides a high density inductively coupled plasmachamber in which a cleaning process is performed efficiently.

What is claimed is:
 1. A chamber for operating on a workpiece,comprising:a) an enclosed chamber adapted to contain a gas; b) aninductive coil in electromagnetic communication with an interior of thechamber when energized; and c) a capacitor in electrostaticcommunication with the interior of the chamber when energized.
 2. Thechamber as specified in claim 1, further comprising a means foreliminating capacitive coupling during a generation of an inductivelycoupled plasma in the chamber.
 3. The chamber as specified in claim 1,whereina) an inductively coupled plasma is generated in the chamberduring an operation performed on the workpiece; and b) wherein acapacitively coupled plasma is generated during a cleaning of thechamber.
 4. The chamber as specified in claim 3, further comprising ameans for eliminating capacitive coupling during a generation of theinductively coupled plasma.
 5. The chamber as specified in claim 1,further comprising a means for eliminating capacitive coupling in theenclosed chamber.
 6. An apparatus, comprising:a) at least two wallsspaced relative to one another, a first of said walls at least partiallydefining an enclosed chamber adapted to contain a plasma; b) a capacitorelectrode positioned between said walls; and c) an inductor coil inelectromagnetic communication with an interior of the chamber whenenergized.
 7. The apparatus as specified in claim 6, wherein saidcapacitor electrode capacitively couples a potential to a plasma in theenclosed chamber during a cleaning process.
 8. The apparatus asspecified in claim 6, wherein the capacitor electrode comprises a liquidwhich is removable from its position between said walls.
 9. Theapparatus as specified in claim 8, wherein said liquid is electricallyconductive.
 10. The apparatus as specified in claim 6, wherein thecapacitor electrode comprises a material of variable conductivity. 11.The apparatus as specified in claim 10, wherein the material of variableconductivity is electrically insulative during electromagneticinduction.
 12. The apparatus as specified in claim 10, where thematerial of variable conductivity is electrically conductive duringcleaning of the enclosed chamber.
 13. The apparatus as specified inclaim 10, further comprising a temperature control unit for regulating atemperature of said material of variable conductivity, wherein aconductivity of said material of variable conductivity is dependent ontemperature.
 14. The apparatus as specified in claim 10, furthercomprising a means for supplying ultrasonic energy to said material ofvariable conductivity to change a conductivity thereof.
 15. Theapparatus as specified in claim 10, further comprising a means forsupplying light energy to said material of variable conductivity tochange a conductivity thereof.
 16. The apparatus as specified in claim10, wherein said material of variable conductivity is a polymer.
 17. Theapparatus as specified in claim 10, wherein a doping of said material ofvariable conductivity is varied to change a conductivity thereof. 18.The apparatus as specified in claim 6, wherein said capacitor electrodeis connectable to a voltage supply.